Tanks that store compressed gas are used in a variety of commercial, industrial, recreational, governmental, and healthcare applications and environments. In almost all cases, the tanks are refillable and reusable over the course of their useful life. Regardless of the type of tank and the gas it is intended to store, compressed-gas tanks are subject to a variety of regulations governing tank identification, use, and safety issues.
Traditionally, the filling or refilling of reusable compressed-gas tanks was a manual operation prone to operator error as well as being inherently dangerous to a refilling operator. More recently, “radio frequency identification” (RFID) tags have been affixed to tanks to help identify important information related to the tank, e.g., the tank's identification, purpose, owner, minimum/maximum fill pressures, tank filling parameters, operating pressures, type of gas the tank is designed to store, storage environment information/regulations, tank test and/or certification dates, tank end-of-life date, etc. Typically, the RFID tag is read prior to some type of manual or automated filling operation. The information read from the RFID tag is used to improve the efficiency and safety associated with the filling operation.
In terms of compressed-gas tank filling operations, conventional RFID tag reading operations introduce efficiency problems and can introduce safety concerns. With respect to efficiency, RFID tag reading relies on proper manual movement/positioning of a manually-manipulated RFID reader, or a properly positioned fixed-location RFID reader. At a minimum, improper RFID reader positioning leads to delays in a tank refilling operation. To combat this issue, higher-power RFID readers (e.g., on the order of 2 watts or more) are relied upon to reduce the reader's sensitivity to reader-to-tag positioning. Unfortunately, the use of higher-power RFID readers introduces potential safety issues.
In terms of safety, it is relevant that most compressed-gas tank-filling operations involve the presence of numerous tanks in an environment equipped to perform the tank filling operations. In these multi-tank environments, when operators rely on higher-power RFID readers (e.g., on the order of 2 watts or more) to reduce RFID positioning concerns relative to an RFID tag as described above, crosstalk between nearby RFID tags can cause incorrect tag-to-tank associations that are subsequently relied upon by a filling operator or an automated filling machine. When this type of error occurs in either a manual or automated tank filling operation, the results can be disastrous as a refilling operator/machine relies on the information it receives from its reader to institute a tank filling operation. That is, an incorrect tag-to-tank association can cause a tank to be over or under pressurized, can cause an out-of-certification tank to be filled, etc. Furthermore, higher-power RFID readers can generate error warnings when operated near electrically-conductive structures. At a minimum, the generation of such error warnings affects the efficiency of a tank filling operation.